1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus in which a cartridge is detachably mounted in an apparatus main body and which forms an image on a recording medium.
Here, the electrophotographic image forming apparatus is an apparatus that forms an image on a recording medium using an electrophotographic image forming process. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer and an LED printer), a facsimile machine, and a word processor. The recording medium is a medium on which an image is formed by the electrophotographic image forming apparatus, examples of which include paper and an OHT (overhead transparency) sheet.
2. Description of the Related Art
A known image forming apparatus (electrophotographic image forming apparatus) using an electrophotographic image forming process in the related art employs a process cartridge system. The process cartridge system is such that a process cartridge in which a photosensitive drum (electrophotographic photosensitive drum), a developing roller that acts on the photosensitive drum, and a developing unit that accommodates toner for use in image formation are integrated to form a single unit is detachably mounted in an apparatus main body. The process cartridge system allows a user to perform maintenance of the apparatus by himself or herself without the help of a serviceman. Therefore, the process cartridge system is widely used in electrophotographic image forming apparatuses. In addition to the foregoing process cartridge system, there are various kinds of cartridge system. For example, there are a developing cartridge system in which a developing roller and toner are accommodated and a toner cartridge system in which only toner is accommodated. An optimum system is selected from them in consideration of the apparatus configuration, cost, etc.
An example of known electrophotographic image forming apparatuses has a configuration in which a scanner unit serving as an exposing unit is mounted to a covering member that opens and closes an opening for mounting and demounting a plurality of cartridges (U.S. Pat. No. 7,356,283). With this configuration, when the covering member is opened to mount or demount the cartridges, the scanner unit retracts, and thus, the ease of operation for mounting and demounting the cartridges can be improved.
U.S. Pat. No. 7,356,283 discloses an image forming apparatus capable of color image formation. In this image forming apparatus, a plurality of cartridges are disposed next to each other diagonally above and below.